On the assumption that on a given day, Lidge is more likely to give up runs than Clippard (just for discussion sake - I'm not assuming that), if my starter goes seven shutout innings and then he's done, it is vitally important to me that the guy pitching the eighth shuts them down. It's a way of saying, you've faced our best for seven innings, but just because he's done, your not off the hook. Or conversely, if you get seven shutout innings, replace the starter, and the eighth inning pitcher blows the lead, what could be more demoralizing.
So I think I'm with Davey on this one. Clippard may be too valuable in his current role to mess around with.
Lidge needs to get the job done in the ninth, and I think he will.